Soldiers conducting military operations have a need to gain entry into reinforced buildings and through reinforced walls. Conventionally, this is done by breaching a hole that is sufficiently large for a man to crawl through, i.e., approximately 30 to 40 inches in diameter. Typical reinforced walls are constructed of concrete and feature two layers of half-inch diameter steel reinforcement (rebar) on a 12-inch grid.
Prior art addressed explosive wall-breaching. Prior art employs either a high-explosive charge placed on the wall or a series of linear shaped charges (LSC) or explosively-formed fragments (EFF) placed in close proximity thereto. High-explosives placed in contact with a steel reinforced concrete (SRC) wall are very effective in removing concrete, but the rebar remains virtually undamaged. LSC and EFF charge arrays are very effective in cutting exposed steel members, such as rebar, but are relatively ineffective against concrete unless large (heavy) charge weights are employed. Prior art does not provide the combined effects of a high-explosive charge to remove concrete and an array of LSC or EFF to cut resultant exposed rebar in one application of a lightweight device suitable for ready carry by personnel or small robots.
Prior art includes: U.S. Pat. No. 4,493,260, Annular Shaped Charge for Breaching Masonry Walls, to Foster; U.S. Pat. No. 4,499,828, Barrier Breaching Device, to Honodel; U.S. Pat. No. 4,856,430, Wall Breaching Apparatus, to Gibb et al.; U.S. Pat. No. 6,477,959, Wall Breaching Warhead, to Ritman et al.; and United States patent application, publication no. 2005/0126420 A1, Wall Breaching Apparatus and Method, to Givens et al.
The '959, '828 and '260 patents describe methods and devices for breaching non-reinforced masonry-type walls only. These do not have capacity to produce a clear breach opening through SRC walls. The '430 patent facilitates breaching a thick wall, but does not have the capacity to breach SRC walls. One embodiment of the '420 patent application permits breaching reinforced walls, but weighs “typically less than about 60 pounds” and “includes the steps of providing a metal lined linear shaped charge having a weight of less than about 60 pounds.” Modern military doctrine limits “man-portable” devices to a weight of not more than about 35 pounds. Further, the '420 device states that “the metal jet cuts at least about 10% to 75% of the cut reinforcement at one location and the remainder at two locations.” Practical experience has shown that this performance will not, in most cases, provide sufficient cutting of steel reinforcement to allow personnel ready access through the resultant opening. In addition, location of the reinforcement cuts resultant from employment of the '420 device is not specified. The optimal location for such cuts is near the perimeter of the resultant opening so as to maximize the size of the opening.
As noted above, conventional methods of breaching such walls with “man-packable” (lightweight) explosives employ two separate operations: placement and detonation of an explosive charge on the wall to remove the concrete, followed by a second operation to cut the exposed steel reinforcement. Cutting of the steel reinforcement is accomplished either by placing additional explosive charges directly on the exposed steel reinforcement at numerous locations to cut the individual steel reinforcement, or by shooting the individual steel reinforcements using a rifle equipped with a special adapter which allows the end of the rifle to be placed against the steel reinforcement to be cut. Either method requires soldiers, or possibly robots, to perform breaching operations at the wall twice, essentially doubling exposure. In addition, these methods do not allow access through the wall immediately after the initial explosive detonation. Thus, the element of surprise is lost in pressing an attack through the opening. The additional time required for the steel reinforcement-cutting operation also provides hostiles time to recover from blast effects of the initial detonation. Thus, a need exists for cleanly breeching a reinforced wall with but a single action on the part of personnel or robots.